The majority of Americans have no clear idea what “sell by” labels are trying to tell them. But after 40 years of letting us guess, the grocery industry has made moves to clear up the confusion.

On Wednesday, the Food Marketing Institute and the Grocery Manufacturers Association, the two largest trade groups for the grocery industry, announced that they’ve adopted standardized, voluntary regulations to clear up what product date labels mean. Where manufacturers now use any of 10 separate label phrases, ranging from “expires on” to “better if used by,” they’ll now be encouraged to use only two: “Use By” and “Best if Used By.”

The former is a safety designation, meant to indicate when perishable foods are no longer good. “Best if Used By” is a quality descriptor — a subjective guess of when the manufacturer thinks the product should be consumed for peak flavor.

That's what most "use-by" dates indicate now, though studies have shown that many consumers believe they signal whether a product is okay to eat. In fact, it's totally fine to eat a product even well after its so-called expiration date.

These dates typically indicate one of two things: a message from the manufacturer to the grocery store, telling the store when the product will look best on shelves, or a subjective measure — often little more than a guess — of when consumers will most “enjoy” the product. Methods for setting those dates have been left to manufacturers, rather like the phrasing of the labels themselves. But when consumers see a date labeled “use by” (or, even worse, not labeled at all) they often tend to assume that it's a food-safety claim, regulated by some objective standard.

Both the Department of Agriculture and a coalition of environmental groups have been urging the industry to clear this up. In addition to costing average Americans, in the form of prematurely tossed groceries, the waste represents a significant use of landfill space and source of greenhouse gas emissions.

“I think it’s huge. It’s just an enormous step,” said Emily Broad-Leib, the director of Harvard’s Food Law and Policy Clinic. “It’s still a first step — but it’s very significant.”

Advocates and environmentalists have been warning for years that many people interpret date labels as a sign that food is no longer good to eat. As a result, one industry survey found, 91 percent of consumers have mistakenly thrown away past-date food, when the label only signals the manufacturer's guess at its peak quality.

Shoppers shouldn’t expect to see the new labels the next time they buy groceries; the change won’t be immediate. While FMI and GMA are urging manufacturers and retailers to make it now, they have until July 2018. Even then, the standards are voluntary, so there’s no guarantee that they’ll be adopted by every single company.

Some states also have labeling regulations that preempt the industry standards. In Montana, for instance, milk must come with a “sell by” label. That means milk in the state will still say “sell by,” even if every other product gets the new labels.

Still, a number of major manufacturers have already signaled their enthusiasm, including Walmart, the largest seller of American groceries. And both FMI and GMA are expecting to see widespread adoption, in part because the standards were written by a working group comprised of representatives from large food companies.

The voluntary standards are also a way to influence, or preempt, pending federal regulation; there has been growing interest in a federal standard for label dates, which would both align the contradictory patchwork of state rules and guarantee corporate compliance. Last May, Sen. Richard Blumenthal (D-Conn.) and Rep. Chellie Pingree (D-Maine) introduced legislation that would standardize both date labels and food donation laws. They’re expected to reintroduce the bill in the coming weeks. In mid-December, the USDA also published nonbinding guidance that encouraged manufacturers to switch to the “Best if Used By” phrasing.

This all delights Broad-Leib, who made similar policy recommendations in a 2013 report with the Natural Resources Defense Council. According to NRDC, Americans throw $218 billion worth of food away each year. The anti-food-waste coalition ReFED estimates that 398,000 tons, or $1.8 billion, could be saved through standardized date labels.

Follow the journey of a strawberry from the farm to the refrigerator to understand all that it takes to bring your food to you. (Ad Council/Natural Resources Defense Council)

Of course, that is just a drop in the waste bucket: To make a real dent in America’s food waste problem, Broad-Leib said, more will have to be done. The Food Law and Policy Clinic is arguing for several federal interventions, including policy changes that make it easier for companies and farms to donate food and incentives to encourage them to do so. [Some of this appears in the Food Donation Act of 2017, which Rep. Marcia Fudge (D-Ohio) introduced a week ago.]

Broad-Leib would also like to see the Department of Agriculture designate more funds for local composting and anaerobic facilities, as well as education campaigns for consumers. NRDC and the Ad Council are currently running one such campaign, called “Save the Food.”